/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.buffer;

import io.netty.util.ReferenceCounted;
import io.netty.util.internal.StringUtil;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;

/**
 * An {@link InputStream} which reads data from a {@link ByteBuf}.
 * <p>
 * A read operation against this stream will occur at the {@code readerIndex} of its underlying
 * buffer and the {@code readerIndex} will increase during the read operation.  Please note that it
 * only reads up to the number of readable bytes determined at the moment of construction.
 * Therefore, updating {@link ByteBuf#writerIndex()} will not affect the return value of {@link
 * #available()}.
 * <p>
 * This stream implements {@link DataInput} for your convenience. The endianness of the stream is
 * not always big endian but depends on the endianness of the underlying buffer.
 *
 * @see ByteBufOutputStream
 */
public class ByteBufInputStream extends InputStream implements DataInput {

  private final ByteBuf buffer;
  private final int startIndex;
  private final int endIndex;
  private boolean closed;
  /**
   * To preserve backwards compatibility (which didn't transfer ownership) we support a conditional
   * flag which indicates if {@link #buffer} should be released when this {@link InputStream} is
   * closed. However in future releases ownership should always be transferred and callers of this
   * class should call {@link ReferenceCounted#retain()} if necessary.
   */
  private final boolean releaseOnClose;

  /**
   * Creates a new stream which reads data from the specified {@code buffer} starting at the current
   * {@code readerIndex} and ending at the current {@code writerIndex}.
   *
   * @param buffer The buffer which provides the content for this {@link InputStream}.
   */
  public ByteBufInputStream(ByteBuf buffer) {
    this(buffer, buffer.readableBytes());
  }

  /**
   * Creates a new stream which reads data from the specified {@code buffer} starting at the current
   * {@code readerIndex} and ending at {@code readerIndex + length}.
   *
   * @param buffer The buffer which provides the content for this {@link InputStream}.
   * @param length The length of the buffer to use for this {@link InputStream}.
   * @throws IndexOutOfBoundsException if {@code readerIndex + length} is greater than {@code
   * writerIndex}
   */
  public ByteBufInputStream(ByteBuf buffer, int length) {
    this(buffer, length, false);
  }

  /**
   * Creates a new stream which reads data from the specified {@code buffer} starting at the current
   * {@code readerIndex} and ending at the current {@code writerIndex}.
   *
   * @param buffer The buffer which provides the content for this {@link InputStream}.
   * @param releaseOnClose {@code true} means that when {@link #close()} is called then {@link
   * ByteBuf#release()} will be called on {@code buffer}.
   */
  public ByteBufInputStream(ByteBuf buffer, boolean releaseOnClose) {
    this(buffer, buffer.readableBytes(), releaseOnClose);
  }

  /**
   * Creates a new stream which reads data from the specified {@code buffer} starting at the current
   * {@code readerIndex} and ending at {@code readerIndex + length}.
   *
   * @param buffer The buffer which provides the content for this {@link InputStream}.
   * @param length The length of the buffer to use for this {@link InputStream}.
   * @param releaseOnClose {@code true} means that when {@link #close()} is called then {@link
   * ByteBuf#release()} will be called on {@code buffer}.
   * @throws IndexOutOfBoundsException if {@code readerIndex + length} is greater than {@code
   * writerIndex}
   */
  public ByteBufInputStream(ByteBuf buffer, int length, boolean releaseOnClose) {
    if (buffer == null) {
      throw new NullPointerException("buffer");
    }
    if (length < 0) {
      if (releaseOnClose) {
        buffer.release();
      }
      throw new IllegalArgumentException("length: " + length);
    }
    if (length > buffer.readableBytes()) {
      if (releaseOnClose) {
        buffer.release();
      }
      throw new IndexOutOfBoundsException("Too many bytes to be read - Needs "
          + length + ", maximum is " + buffer.readableBytes());
    }

    this.releaseOnClose = releaseOnClose;
    this.buffer = buffer;
    startIndex = buffer.readerIndex();
    endIndex = startIndex + length;
    buffer.markReaderIndex();
  }

  /**
   * Returns the number of read bytes by this stream so far.
   */
  public int readBytes() {
    return buffer.readerIndex() - startIndex;
  }

  @Override
  public void close() throws IOException {
    try {
      super.close();
    } finally {
      // The Closable interface says "If the stream is already closed then invoking this method has no effect."
      if (releaseOnClose && !closed) {
        closed = true;
        buffer.release();
      }
    }
  }

  @Override
  public int available() throws IOException {
    return endIndex - buffer.readerIndex();
  }

  @Override
  public void mark(int readlimit) {
    buffer.markReaderIndex();
  }

  @Override
  public boolean markSupported() {
    return true;
  }

  @Override
  public int read() throws IOException {
    if (!buffer.isReadable()) {
      return -1;
    }
    return buffer.readByte() & 0xff;
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    int available = available();
    if (available == 0) {
      return -1;
    }

    len = Math.min(available, len);
    buffer.readBytes(b, off, len);
    return len;
  }

  @Override
  public void reset() throws IOException {
    buffer.resetReaderIndex();
  }

  @Override
  public long skip(long n) throws IOException {
    if (n > Integer.MAX_VALUE) {
      return skipBytes(Integer.MAX_VALUE);
    } else {
      return skipBytes((int) n);
    }
  }

  @Override
  public boolean readBoolean() throws IOException {
    checkAvailable(1);
    return read() != 0;
  }

  @Override
  public byte readByte() throws IOException {
    if (!buffer.isReadable()) {
      throw new EOFException();
    }
    return buffer.readByte();
  }

  @Override
  public char readChar() throws IOException {
    return (char) readShort();
  }

  @Override
  public double readDouble() throws IOException {
    return Double.longBitsToDouble(readLong());
  }

  @Override
  public float readFloat() throws IOException {
    return Float.intBitsToFloat(readInt());
  }

  @Override
  public void readFully(byte[] b) throws IOException {
    readFully(b, 0, b.length);
  }

  @Override
  public void readFully(byte[] b, int off, int len) throws IOException {
    checkAvailable(len);
    buffer.readBytes(b, off, len);
  }

  @Override
  public int readInt() throws IOException {
    checkAvailable(4);
    return buffer.readInt();
  }

  private StringBuilder lineBuf;

  @Override
  public String readLine() throws IOException {
    if (!buffer.isReadable()) {
      return null;
    }
    if (lineBuf != null) {
      lineBuf.setLength(0);
    }

    loop:
    do {
      int c = buffer.readUnsignedByte();
      switch (c) {
        case '\n':
          break loop;

        case '\r':
          if (buffer.isReadable() && (char) buffer.getUnsignedByte(buffer.readerIndex()) == '\n') {
            buffer.skipBytes(1);
          }
          break loop;

        default:
          if (lineBuf == null) {
            lineBuf = new StringBuilder();
          }
          lineBuf.append((char) c);
      }
    } while (buffer.isReadable());

    return lineBuf != null && lineBuf.length() > 0 ? lineBuf.toString() : StringUtil.EMPTY_STRING;
  }

  @Override
  public long readLong() throws IOException {
    checkAvailable(8);
    return buffer.readLong();
  }

  @Override
  public short readShort() throws IOException {
    checkAvailable(2);
    return buffer.readShort();
  }

  @Override
  public String readUTF() throws IOException {
    return DataInputStream.readUTF(this);
  }

  @Override
  public int readUnsignedByte() throws IOException {
    return readByte() & 0xff;
  }

  @Override
  public int readUnsignedShort() throws IOException {
    return readShort() & 0xffff;
  }

  @Override
  public int skipBytes(int n) throws IOException {
    int nBytes = Math.min(available(), n);
    buffer.skipBytes(nBytes);
    return nBytes;
  }

  private void checkAvailable(int fieldSize) throws IOException {
    if (fieldSize < 0) {
      throw new IndexOutOfBoundsException("fieldSize cannot be a negative number");
    }
    if (fieldSize > available()) {
      throw new EOFException("fieldSize is too long! Length is " + fieldSize
          + ", but maximum is " + available());
    }
  }
}
